1. Field
The present specification generally relates to methods for separating glass and, more specifically, to methods for laser scribing and breaking separating thin glass substrates.
2. Technical Background
Thin glass substrates have a variety of applications in consumer electronic devices. For example, such glass substrates may be used as cover sheets for LCD and LED displays incorporated in mobile telephones, display devices such as televisions and computer monitors and various other electronic devices. Cover sheets used in such devices may be formed by sectioning or separating a large glass substrate into a plurality of smaller glass substrates using various laser cutting techniques.
For example, thin glass substrates having a thickness of greater than about 0.7 mm may be separated by scribe-and-break techniques using a laser to form a vent partially through the thickness of the glass and thereafter applying a mechanical force to the glass substrate to separate the glass substrate into multiple pieces. The benefits of such scribe-and-break techniques are high processing speed and good edge attributes such as edge quality and edge straightness in the finished glass pieces without generating glass chips during the scribing process.
In a typical laser scribe-and-break process a laser is used to heat the glass substrate along a line of separation. The heated glass substrate is then quenched with a water jet which is positioned behind and spaced apart from the trailing edge of the beam of the laser along the line of separation. The quenching generates a tensile stress which is perpendicular to the line of separation. When the tensile stress is applied to a defect introduced in the glass substrate, a vent is generated and propagates in the direction of the line of separation. Thereafter, the glass substrate may be separated mechanically along the vent.
While such techniques are effective for glass substrates having thicknesses of about 0.7 mm or greater, such techniques may not be readily applicable to glass substrates having thicknesses of less than about 0.7 mm as irreversible full body separation often occurs upon quenching (i.e., the vent propagates substantially through the thickness of the glass such that the glass separates). This uncontrolled separation generally leads to poor edge characteristics compared to the scribe and break process. Moreover, full body separation of the substrate along the line of separation prevents the formation of additional, intersecting vents in a single glass substrate.
Accordingly, a need exists for alternative methods for separating thin glass substrates.